Specimen stages for electron microscopes

ABSTRACT

A specimen stage for an electron microscope having a wire-driven gimbal assembly. The assembly is so designed that there is no interaction between the tilting of the inner and outer gimbals. The drive for the gimbals comprises two wires, each of which is attached at one end to a drive pulley and at its outer end, after passing around a guide pulley pivoted about the outer gimbal axis, is coupled to the inner gimbal. Thus, when the outer gimbal is tilted, the wires wind on to or off of the guide pulleys, causing the drive pulley to move towards or away from the gimbals, but with substantially no tilting of the inner gimbal.

Lucas [75] inventor:

[54] SPECIMEN STAGES FOR ELECTRON MICROSCOPES Jeffrey H. Lucas, Rickling, near Saffron Walden, Essex, England [73] Assignee: Associated Electric Limited, London, England 1221 Filed: May 21,1971 [211 Appl.No.: 145,694

[30] Foreign Application Priority Data [58] Field of Search........2 5 0/49.5 R, 49.5 A, 49.5 B, 250/515; 33/226 [56] References Cited UNITED STATES PATENTS 3,086,112 4/1963 Riecke 250 4955 lndustires 1 1' Jan. 30, 1973 3,566,1ll 2/l97l Harm ..-...250/5 I .5 3,486,02l l2/l969 Honme ..250/5l.5 1

Primary ExaminerArchie R. Borchelt Assistant ExaminerD. C. Nelms Attorney-Watts, Hoffmann, Fisher & Heinke [57] ABSTRACT A specimen stage for an'elec tron microscope having a wire-driven gimbal assembly. The assembly is so designed that there is no interaction between the tilting of the inner and outer gimbals. The drive for the gimbals comprises two wires, each of which is attached at one end to a drive pulley and at its outer end, after passing around a guide pulley pivoted about the outer gimbal axis, is coupled to the inner gimbal. Thus, when the outer gimbal is tilted, the wires wind on to or off of the guide pulleys, causing the drive pulley to move towards or away from the gimbals, but with substantially no tilting of the inner gimbal.

21 Claims, 7 Drawing Figures PATENTEI] JAN 3 0 I975 SHEET 10F 6 PATENTED JAN 30 I973 SHEET b 0F 6 FATENTEDJAN 30 ms SHEET 5 [IF 6 PATENTEDJM 30 I973 SHEET 8 [IF 6 SPECIMEN STAGES FOR ELECTRON MICROSCOPES This invention relates to specimen stages for electron microscopes.

One known kind of specimen stage for an electron microscope comprises a first member mounted pivotally about an axis on a support, a second member adapted to receive the specimen and mounted pivotally about an axis on the first member, said axes being mutually inclined, first tilting means for tilting the first member about its axis with respect to the support, and second tilting means for tilting the second member about its axis with respect to the first member. Such a specimen stage allows the specimen to be tilted for viewing from different angles.

One object of the present invention is to provide a novel specimen stage of the kind specified wherein there is little or no interaction between the operations of said first and second tilting means, i.e. wherein application of tilt to the first member does not affect substantially the orientation of the second member with respect to the first member.

According to one aspect of the invention, in a specimen stage of the kind specified, the second tilting means comprises two flexible drive members, for example wires, each of which is coupled at one end to drive means mounted on said support for movement along a path with respect to the support and, after being guided around the axis of said first member by suitable guide means, is coupled at its other end to the second member, the flexible drive members thus serving to convey drive from the drive means to tilt the second member respectively in opposite senses with respect to the first member, the drive means being biassed in one direction along said path so as to take up any slack in the flexible drive members, and the arrangement being such that, when the first member is tilted, the flexible drive members wind on to or off of said guide means causing the drive means to move along its path with, substantially no movement with respect to the first member of those portions of the flexible drive members coupled to the second member and hence substantially no tilting of the second member with respect to the first member.

Said flexible drive members may comprise respective portions of a single flexible member.

Conveniently said drive means comprises a drive pulley each said flexible drive member being secured-at said one end to a point on the rim of the pulley. Conveniently, said guide means comprises a pair of pulleys, pivoted about the axis of said first member.

Another object of the present invention is to provide a specimen stage for an electron microscope which allows large angles of tilt to be produced.

Thus, according to a second aspect of the invention, in a specimen stage of the kind specified, said first and second tilting means comprise flexible drive members, for example wires, coupled at one end to respective drive means mounted on said support, and at the other end coupled respectively to said first and second members.

One electron microscope, including a specimen stage in accordance with the invention, will now be described, by way of example, with reference to the accompanying drawings, of which:

FIG. 1 is a schematic diagram of the electron microscope;

FIG. 2 is a diagrammatic view of the moving parts of the assembly;

FIG. 3 is an exploded view of the assembly;

FIG. 4 is a perspective view of the assembly;

FIG. 5 is a view of the assembly mounted in the specimen stage of the electron microscope; and

FIGS. 6 and 7 are diagrams illustrating the principle of operation of the assembly.

Referring to FIG. 1, the microscope comprises an evacuable casing 101 in which is housed a plurality of electron optical lenses, comprising two condenser lenses 102, 103, an objective lens 104, and three projector lenses 105, 106, 107. These lenses are represented schematically only in the figure, and in particular the shapes of their polepieces and lens gaps are not indicated.

A specimen stage 108 is located inside the casing 101 between the condenser lenses 102, 103 and the objective lens 104, and is arranged to position a specimen in the lens gap of the objective lens 104. The stage 108 will be described below in greater detail.

Electrons are produced by means of an electron gun 109 and travel along a path through the lenses 102-107 to produce a magnified image of the specimen on a screen 111. Beam positioning means 112 are provided for adjusting the lateral position of the beam before it strikes the specimen.

Referring now to FIGS. 2 and 3, the specimen stage of the microscope comprises a gimbals assembly comprising a generally tubular support 1 in one end of which is pivotally mounted an outer gimbal ring 2, arranged to tilt about an axis 3 with respect to the support. Within the outer gimbal 2 is pivotally mounted an inner gimbal ring 4, arranged to tilt with respect to the outer gimbal 2, about an axis 5 at right angles to the axis 3.

A specimen holder (not shown) adapted to hold a specimen grid, can be secured on the inner gimbal 4, by means ofa circlip.

A drive pulley 6 is pivotally mounted on a bracket 7 which extends from the end of the support 1 opposite the end within which the gimbals 2, 4 are mounted, the axis of rotation of the pulley 6 being parallel to the outer gimbal axis 3. A second drive pulley 8 is pivotally mounted on a carriage 9, which slides in a slot 10 in a bracket 11 which also extends from the support 1, the carriage being biassed in a direction away from the gimbals 2, 4 by a spring 12. The axis of rotation of the pulley 8 is at right angles to the axis of the pulley 6.

The drive pulleys 6, 8 serve to drive the tilt motions of the outer and inner gimbals respectively, as will be hereinafter described in detail.

Referring now to FIGS. 3 and 4, the support 1 fits within a bore 13 in an outer support 14. A pair of push rods 15, 16 are mounted in grooves 17, 18 in the outer support 14, running at right angles to each other, each rod l5, 16 being associated with one of the pulleys 6, 8, and having a slot 19 in which fits a pin 20 on the associated pulley. Thus, as the push rods 15, 16 are slid longitudinally in their grooves 17, 18, the pulleys 6, 8 are caused to rotate. The push rods 15, 16 are held in their grooves by a stirrup 41 which is attached by screws to the top of the outer support 14.

Referring now to FIG. 5, the support 1 and outer support 14 together form an specimen cartridge which can be mounted in the specimen stage 21 of the electron microscope, by means of an insertion mechanism (not shown) which engages with the stirrup 41. Drive is transmitted to the pushrods 15, 16 by means of respective worm gear mechanisms 22, 23 which are coupled by way of universal telescopic joints 42 to drive shafts 24, 25 which in turn are connected by way of universal joints to controls external of the microscope column (not shown). The joints 42 allow for transverse linear movement of the stage 21, by means of stage positioning controls (not shown).

Referring now to FIG. 6 drive is transmitted between the pulley 6 and the outer gimbal 2 by means of a drive wire 26, one end of which is secured at a point 27 on the rim of the pulley 6, and the other end of which is secured at a point 28 on the rim of a pulley 29 which is rigidly attached to the outer gimbal 2 on the axis 3. In this way, the motion of the specimen stage drive shaft 24 is transmitted in a substantially linear manner, via the push rod 15, the pulley 6, the wire 26 and the pulley 29 to the outer gimbal 2; i.e. the angle of tilt of the outer gimbal 2 about its axis is substantially proportional to the angle of rotation of the drive shaft 24.

Referring now to FIG. 7, drive is transmitted between the drive pulley 8 and the inner gimbal 4 by means of drive wires 30, 31. One end of drive wire 30 is secured at a point 32 on the rim of the drive pulley 8, the wire 30 then passing around a guide pulley 33, pivotally mounted on the outer gimbal 2 on the axis 3, and finally passing around the outside surface of the outer gimbal and being secured at a point 34 on the rim of a tilt pulley 35. Similarly, one end of drive wire 31 is secured to the rim of the drive pulley 8 at a point 36, the wire 31 then passing around a guide pulley 37, pivotally mounted on the outer gimbal 2 about the axis 3, and finally passing around the outside surface of the outer gimbal and being secured to the point 34 on the pulley 35. The wires 30, 31 pass around rollers 43 on a guide plate 38 mounted below the pulley 8, which serve to guide the wires on to the rim of the pulley 8.

Since both wires 30, 31 are secured to the same point 34 on the tilt pulley 35, they could conveniently be joined at that point, so that they together constitute a single length of wire.

The tilt pulley is rigidly connected to the inner gimbal 4. Thus, when the drive pulley 8 is rotated in a first direction, indicated by the arrow 39, drive is transmitted to the tilt pulley 34 by the wire 31, and the inner gimbal 4 is tilted in a first sense about the axis 5 with respect to the outer gimbal, as shown in FIG. 7. If the drive pulley 8 is rotated in the opposite direction, drive is transmitted to the pulley 34 by the wire 30, causing the inner gimbal 4 to be tilted in the opposite sense.

ln this way, the motion of the specimen stage drive shaft 25 is transmitted in a substantially linear manner via the push rod 16, the pulley 8, the wires 30, 31, and the pulley 35, to the inner gimbal 4; Le. the angle of tilt of the inner gimbal about its axis with respect to the outer gimbal is substantially proportional to the angle of rotation ofthe drive shaft 25.

When the outer gimbal 2 is rotated about its axis 3, the wires 30, 31 are wound onto, or unwound from, the guide pulleys 33, 37, causing the drive pulley to move towards or away from the gimbals 2, 4. However, it will be seen that there is no movement with respect to the outer gimbal 4 of the portions of the wires 30, 31 lying between the guide pulleys 33, 37 and the tilt pulley 35, and therefore there is no rotation of the inner gimbal 4 with respect to the outer gimbal 2.

Thus it will be seen that there is no interaction between the tilting of the inner and outer gimbals.

A return spring 40 is provided for push rod 16, while the spring 12 applies a return motion for the rod 15. Al ternatively, a separate return spring may be provided for the rod 15.

The wire drive system herein described by way of example, in addition to having the advantages of being a non-interactive system, and a linear system, has the further advantage that large angles of tilt can be produced, for example, of the order of in any direction. In principle, the only inherent limitation to the maximum angle of tilt obtainable is the shadowing effect caused by the thickness of the specimen holder which supports the specimen grid.

It will be appreciated that, instead of wires, other kinds of flexible drive members could be used to tilt the gimbals, such as, for example, nylon threads, metal ribbon, or chain.

It will be appreciated that the invention when applied to electron microscopes is applicable to scanning electron microscopes as well as to the non-scanning kind of electron microscope. In addition, although the specimen stage described above by way of example is a so-called top entry" stage, it will be appreciated that the invention can also be applied to so-called side entry stages.

What is claimed is:

1. In an electron microscope, an improved specimen stage comprising:

a. a support structure;

b. a first gimbal member carried by said support structure and pivotally mounted for tilting about a first axis;

0. a second gimbal member carried by said first gimbal member and pivotally mounted for tilting about a second axis inclined to said first axis;

. first and second tilting means carried by said support structure for respectively tilting said first and second gimbal member about said first and second axes;

c. said first and second tilting means comprising first andv second control means and first and second flexible elongated force transmitting means of the type which may be disposed along a nonlinear path to transmit force between spaced regions along said path; and, 1

f. said first force transmitting means connecting said first control means and said first gimbal member, so that operation of said first control means will correspondingly tilt said first gimbal member, and said second force transmitting means connecting said second control means and said second gimbal member so that operation of said second control means will correspondingly tilt said second gimbal member.

2. The specimen stage of claim 1 additionally including guide means for guiding said second force transmitting means about said first axis of said first gimbal member whereby said second force transmitting means will wind about said first axis when said first gimbal member is tilted, without causing any tilting of said second gimbal member, thereby permitting the tilt of each of said gimbal members to be controlled independently of the other gimbal member.

3. The specimen stage of claim 2 wherein said second control means is mounted on said support for movement along a path with respect to said support, to permit said second force transmitting means to wind about said first axis.

4. The specimen stage of claim 3 additionally including biasing means for biasing said second control means in one direction along said path to take up any slack in said second force transmitting means.

5. The specimen stage of claim 2 wherein each of said force transmitting means comprises a wire.

6. The specimen stage of claim 2 wherein said first and second control means respectively comprise first and second drive pulleys connected respectively with said first and second force transmitting means.

7. The specimen stage of claim 6 additionally including first and second push rods carried by said support means and connected to said first and second drive pulleys whereby translation of said first and second push rods will respectively rotate said first and second drive pulleys.

8. The specimen stage of claim 7 additionally including:

a. pulley means connected to said first gimbal member coaxially with said first axis;

b. said first force transmitting means being connected to said pulley means;

c. whereby rotation of said first drive pulley in a first direction will cause said first force transmitting means to wind about said first drive pulley and to unwind from said pulley means thereby rotating said pulley means and tilting said first gimbal member about'said first axis.

9. The specimen stage of claim 1 wherein said first and second control means are mounted for movement relative to said support and are operative to tilt their respective gimbal members by amounts which are linearly proportional to their respective distances of movement.

10. in an electron microscope, an improved specimen stage comprising:

a. a support structure;

b. a first gimbal member carried by said support structure and pivotally mounted for tilting about a first axis;

c. a second gimbal member carried by said first gimbal member and pivotally mounted for tilting about a second axis, inclined to said first axis;

. first and second tilting means carried by said support structure for respectively tilting said first and second gimbal members about said first and second axis;

e. said second tilting means comprising control means and flexible drive means;

f. said flexible drive means connecting said control means and said second gimbal member so that operation of said control means will correspondingly tilt said second gim bal member; and,

g. guide means for guiding said flexible drive means about said first axis of said first gimbal member whereby said flexible drive means will wind about said first axis when said first gimbal member is tilted, without causing any tilting of said second gimbal member, thereby permitting the tilt of each of said gimbal members to be controlled independently ofthe other gimbal member.

11. The specimen stage of claim 10 wherein said guide means comprises two pulleys rotatably mounted axially about said first axis.

12. The specimen stage of claim 10 wherein said flexible drive means comprises a wire.

13. The specimen stage of claim 10 wherein said control means is mounted on said support for movement along a path with respect to said support, to permit said flexible drive means to wind about said first axis.

14. The specimen stage of claim 13 additionally in-.

cluding biasing means for biasing said control means in one direction along said path to take up any slack in said flexible drive means.

15. The specimen stage of claim 10 wherein said flexibledrive means comprises:

a. a first portion connecting said control means and said second gimbal member, for transmitting operation of said control means in a first sense to tilt said second gimbal member in a first sense.

b. and a second portion connecting said control means and said second gimbal member, for transmitting operation of said control means in a second sense to tilt said second gimbal member in a second sense. I

16. The specimen stage of claim 15 wherein:

a. said guide means comprises two pulleys rotatably mounted axially about said first axis;

b. said first portion of the flexible drive means passing around one said pulley; and,

c. said second portion of the flexible drive means passing around the other said pulley.

17. The specimen stage of claim 10 wherein said control means comprises a drive pulley connected with said flexible drive means.

18. The specimen stage of claim 17 additionally including a push rod carried by said support means and connected to said drive pulley whereby translation of said push rod will rotate said drive pulley.

19. The specimen stage of claim 10 wherein said second control means is mounted for movement relative to said support and is operative to tilt said second gimbal member by an amount which is linearly proportional to the distance of movement of said second control means.

20. An electron microscope comprising:

a. an elongated evacuatable housing;

b. an electron beam source near one end of the housing; I

c. an image producing electron stimulated means near the other end of the housing;

d. a specimen stage positioned intermediate the ends of the housing;

e. electron optical lens means within the housing inv eluding portions for focusing electrons emitted by said source into a beam and bombarding a specimen mounted in said stage, said lens means including other portions for focusing electrons flowing from said specimen onto said image means;

f. said stage including a specimen support and means for tilting the support about a pair of mutually inclined axes;

gr said support being tiltable about each axis through a range having its limits delineated by interference of said specimen support with said electron beam directed on the specimen or said flow of electrons from the specimen to produce an image; and,

b. said tilting means being external of the electron 21. In an electron microscope, an improved specimen stage comprising:

a. a support structure; a b. first and second gimbal members carried by said support structure and pivotally mounted for tilting respectively about first and second mutually inclined axes;

. a specimen holder mounted on one of said gimbal members; and,

. tilting means for independently tilting each of said gimbal members about their pivotal mountings through an angular range great enough that the limitation to the maximum angle of usable tilt when the device is in use is the shadowing effect caused by thickness of said specimen holder. 7

a a a 

1. In an electron microscope, an improved specimen stage comprising: a. a support structure; b. a first gimbal member carried by said support structure and pivotally mounted for tilting about a first axis; c. a second gimbal member carried by said first gimbal member and pivotally mounted for tilting about a second axis inclined to said first axis; d. first and second tilting means carried by said support structure for respectively tilting said first and second gimbal member about said first and second axes; e. said first and second tilting means comprising first and second control means and first and second flexible elongated force transmitting means of the type which may be disposed along a nonlinear path to transmit force between spaced regions along said path; and, f. said first force transmitting means connecting said first control means and said first gimbal member, so that operation of said first control means will correspondingly tilt said first gimbal member, and said second force transmitting means connecting said second control means and said second gimbal member so that operation of said second control means will correspondingly tilt said second gimbal member.
 1. In an electron microscope, an improved specimen stage comprising: a. a support structure; b. a first gimbal member carried by said support structure and pivotally mounted for tilting about a first axis; c. a second gimbal member carried by said first gimbal member and pivotally mounted for tilting about a second axis inclined to said first axis; d. first and second tilting means carried by said support structure for respectively tilting said first and second gimbal member about said first and second axes; e. said first and second tilting means comprising first and second control means and first and second flexible elongated force transmitting means of the type which may be disposed along a nonlinear path to transmit force between spaced regions along said path; and, f. said first force transmitting means connecting said first control means and said first gimbal member, so that operation of said first control means will correspondingly tilt said first gimbal member, and said second force transmitting means connecting said second control means and said second gimbal member so that operation of said second control means will correspondingly tilt said second gimbal member.
 2. The specimen stage of claim 1 additionally including guide means for guiding said second force transmitting means about said first axis of said first gimbal member whereby said second force transmitting means will wind about said first axis when said first gimbal member is tilted, without causing any tilting of said second gimbal member, thereby permitting the tilt of each of said gimbal members to be controlled independently of the other gimbal member.
 3. The specimen stage of claim 2 wherein said second control means is mounted on said support for movement along a path with respect to said support, to permit said second force transmitting means to wind about said first axis.
 4. The specimen stage of claim 3 additionally including biasing means for biasing said second control means in one direction along said path to take up any slack in said second force transmitting means.
 5. The specimen stage of claim 2 wherein each of said force transmitting means comprises a wire.
 6. The specimen stage of claim 2 wherein said first and second control means respectively comprise first and second drive pulleys connected respectively with said first and second force transmitting means.
 7. The specimen stage of claim 6 additionally including first and second push rods carried by said support means and connected to said first and second drive pulleys whereby translation of said first and second push rods will respectively rotate said first and second drive pulleys.
 8. The specimen stage of claim 7 additionally including: a. pulley means connected to said first gimbal member coaxially with said first axis; b. said first force transmitting means being connected to said pulley means; c. whereby rotation of said first drive pulley in a first direction will cause said first force transmitting means to wind about said first drive pulley and to unwind from said pulley means thereby rotating said pulley means and tilting said first gimbal member about said first axis.
 9. The specimen stage of claim 1 wherein said first and second control means are mounted for movement relative to said support and are operative to tilt their respective gimbal members by amounts which are linearly proportional to their respective distances of movement.
 10. In an electron microscope, an improved specimen stage comprising: a. a support structure; b. a first gimbal member carried by said support structure and pivotally mounted for tilting about a first axis; c. a second gimbal member carried by said first gimbal member and pivotally mounted for tilting about a second axis, inclined to said first axis; d. first and second tilting means carried by said support structure for respectively tilting said first and second gimbal members about said first and second axis; e. said second tilting means comprising control means and flexible drive means; f. said flexible drive means connecting said control means and said second gimbal member so that operation of said control means will correspondingly tilt said second gimbal member; and, g. guide means for guiding said flexible drive means about said first axis of said first gimbal member whereby said flexible drive means will wind about said first axis when said first gimbal member is tilted, without causing any tilting of said second gimbal member, thereby permitting the tilt of each of said gimbal members to be controlled independently of the other gimbal member.
 11. The specimen stage of claim 10 wherein said guide means comprises two pulleys rotatably mounted axially about said first axis.
 12. The specimen stage of claim 10 wherein said flexible drive means comprises a wire.
 13. The specimen stage of claim 10 wherein said control means is mounted on said support for movement along a path with respect to said support, to permit said flexible drive means to wind about said first axis.
 14. The specimen stage of claim 13 additionally including biasing means for biasing said control means in one direction along said path to take up any slack in said flexible drive means.
 15. The specimen stage of claim 10 wherein said flexible drive means comprises: a. a first portion connecting said control means and said second gimbal member, for transmitting operation of said control means in a first sense to tilt said second gimbal member in a first sense. b. and a second portion connecting said control means and said second gimbal member, for transmitting operation of said control means in a second sense to tilt said second gimbal member in a second sense.
 16. The specimen stage of claim 15 wherein: a. said guide means comprises two pulleys rotatably mounted axially about said first axis; b. said first portion of the flexible drive means passing around one said pulley; and, c. said second portion of the flexible drive means passing around the other said pulley.
 17. The specimen stage of claim 10 wherein said control means comprises a drive pulley connected with said flexible drive means.
 18. The specimen stage of claim 17 additionally including a push rod carried by said support means and connected to said drive pulley whereby translation of said push rod will rotate said drive pulley.
 19. The specimen stage of claim 10 wherein said second control means is mounted for movement relative to said support and is operative to tilt said second gimbal member by an amount which is linearly proportional to the distance of movement of said second control means.
 20. An electron microscope comprising: a. an elongated evacuatable housing; b. an electron beam source near one end of the housing; c. an image producing electron stimulated means near the other end of the housing; d. a specimen stage positioned intermediate the ends of the housing; e. electron optical lens means within the housing including portions for focusing electrons emitted by said source into a beam and bombarding a specimen mounted in said stage, said lens meAns including other portions for focusing electrons flowing from said specimen onto said image means; f. said stage including a specimen support and means for tilting the support about a pair of mutually inclined axes; g. said support being tiltable about each axis through a range having its limits delineated by interference of said specimen support with said electron beam directed on the specimen or said flow of electrons from the specimen to produce an image; and, h. said tilting means being external of the electron beam bombarding the specimen and the flow of electrons from the specimen at all times when the specimen support is in said range whereby a full range of adjustment is achieved without the tilting mechanism interferring with the production of an image. 